Many of the advantages of reducing or raising the temperature of a body tissue are well known. It has been found particularly desirable to lower the temperature of the body in order to reduce the metabolism of the body. In stroke and several other pathological conditions, lowering the temperature of a body also reduces the permeability of the blood/brain barrier. Reduced body temperature also inhibits release of damaging neurotransmitters and inhibits calcium-mediated effects. Further, reduced body temperature has been found to inhibit brain edema and lower intracranial pressure. These and other advantageous effects of reduced body temperature are known in the art.
Prior art devices and methods affect a thermal change in a body by a systemic approach, meaning that the overall temperature of the entire body is lowered or raised to achieve the advantages noted above. Cooling the body has been particularly effective in surgical applications where reducing metabolism has made it possible to more easily accommodate lengthy operative procedures. An example of this systemic approach includes catheters for transferring heat to or from blood flowing within a patient's vessel. Closed loop heat exchange catheters are also known. Some of the disadvantages of systemic temperature reduction include the stimulation of cardiac arrhythmia, pulmonary edema and coagulopathies. Systemic temperature reduction also results in hypotension and immune suppression.
Further, a systemic approach is not always advantageous when the beneficial effects are desired locally at the focus of the operative procedure and only the disadvantages of temperature reduction are felt throughout the remainder of the body. As such, recent focus has been directed to producing reduced temperature in localized areas of the body, leaving the remainder of the body to function at a normal body temperature. Localized temperature reduction in known devices relies on the control of temperature through a wholly external device, for example using cooling helmets or cooling neck collars to produce localized temperature reduction for the brain. However, there are disadvantages associated with external cooling to affect internal tissue. For example, external methods do not allow a high enough resolution to allow selective tissue cooling. Some of the same disadvantages that are associated with thermally affecting the whole body can occur when using external cooling. When it is advantageous to apply thermal energy to a specified tissue location and not to other regions, the known external devices and their accompanying methods can not adequately accommodate these needs.
Therefore it is desirable to have a device and method for localized temperature control of a body part. Further, it is desirable to provide a way to apply thermal energy to a specific area of tissue, such as the brain, which is not ordinarily directly external to the body in a manner which minimizes trauma and the size of the body opening which must be created to access the tissue area.